CN112689565A

CN112689565A - Pneumatic tire

Info

Publication number: CN112689565A
Application number: CN201980059830.2A
Authority: CN
Inventors: 坂本洋佑; 桑原陵
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2018-09-14
Filing date: 2019-09-11
Publication date: 2021-04-20
Anticipated expiration: 2039-09-11
Also published as: US12005742B2; CN112689565B; JP2020044882A; AU2019339095B2; WO2020054768A1; AU2019339095A1; US20220118796A1; JP6644271B1

Abstract

A pneumatic tire improved in running performance and cut resistance on an unpaved road is provided. A high block (23H) and a low block (23L) having different ridge heights are provided as a side block (23) provided in a side wall region, when a block pair (B) including the high block (23H) and the low block (23L) adjacent to each other in the tire circumferential direction is provided, a part of the high block (23H) and the low block (23L) included in the block pair (B) is brought into contact with each other, a sidewall groove (33) sandwiched by the blocks is provided as a closed groove (33A), a pair of contour lines (a first straight line portion (L1), a second straight line portion (L2) and a third straight line portion (L3)) constituting edge portions on both sides of the top surfaces of the high block (23H) and the low block (23L) in the tire circumferential direction extend in the same direction with respect to an angle difference of 15 DEG or less between the first straight line portions (L1), and any one of the second straight line portions (L2) and the third straight line portion (L3) extend in the same direction with an angle of 15 DEG or less, the second linear portions (L2) and the third linear portions (L3) are extended in directions different from each other.

Description

Pneumatic tire

Technical Field

The present invention relates to a pneumatic tire suitable as a tire for running on unpaved roads, and more particularly to a pneumatic tire having improved running performance and cut resistance on unpaved roads.

Background

In a pneumatic tire intended to run on an uneven, muddy, snow-covered road, sand, rock or other unpaved road, a tread pattern having a large groove area and mainly composed of lateral grooves and blocks having a large edge component is generally used. In addition, the sidewall blocks are provided in the sidewall regions on the outer sides in the tire width direction than the shoulder blocks located at the outermost sides in the tire width direction of the tread portion. In such a tire, traction performance is obtained by engaging projections and depressions made of grooves and blocks provided in the tread portion and the sidewall region into mud, snow, sand, stone, rocks, and the like on the road surface (hereinafter, these are collectively referred to as "mud and the like"), and the driving performance on an unpaved road is improved by preventing the mud and the like from being clogged in the grooves with a large groove area (for example, see patent documents 1 and 2).

When the tires of

patent documents

1 and 2 are compared, the tire of patent document 1 can be said to be a type in which the groove area is relatively small and the running performance on a paved road is also considered. On the other hand, the tire of patent document 2 can be said to be a type of tire having a large groove area, large blocks, and a traveling performance specialized on unpaved roads. Therefore, the former has a lower running performance on unpaved roads than the latter, and the latter tends to have a lower performance in normal running than the former. In recent years, as the performance required of tires has been diversified, unpaved road running tires having performance at an intermediate level between these two types of tires have also been required. Therefore, for example, in the side wall region, a measure for optimizing the shape of the groove or the block to effectively improve the running performance on the unpaved road is required. Further, since a failure such as tip cut (tip cut) is likely to occur when the vehicle travels on an unpaved road, it is also required to improve the cut resistance while the traveling performance on the unpaved road is satisfactorily exhibited.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-007861

Patent document 2: japanese patent laid-open publication No. 2013-119277

Disclosure of Invention

Problems to be solved by the invention

The invention aims to provide a pneumatic tire with improved running performance and cut resistance on an unpaved road.

Means for solving the problems

The pneumatic tire of the present invention for achieving the above object includes: a tread portion extending in a tire circumferential direction and having a ring shape; a pair of sidewall portions disposed on both sides of the tread portion; and a pair of bead portions disposed on the inner side of the sidewall portions in the tire radial direction, wherein a plurality of sidewall grooves extending in the tire radial direction and a plurality of sidewall blocks partitioned by the sidewall grooves and rising from the outer surfaces of the sidewall portions are provided in a sidewall region adjacent to the inner side of the sidewall portions in the tire radial direction at a boundary between the tread portion and the sidewall portions, the sidewall blocks include 2 kinds of blocks each including a high block having a relatively large rising height and a low block having a relatively small rising height, the high blocks and the low blocks are alternately arranged in the tire circumferential direction, and when the high blocks and the low blocks adjacent to each other in the tire circumferential direction are set as a block pair, a part of the high blocks and the low blocks included in the block pair is in contact with each other, whereby the inner end of the sidewall groove located between the high block and the low block included in the block pair in the tire radial direction is closed, in each block pair, a pair of contour lines of the edge portions on both sides in the tire circumferential direction of the top surface of the high block and a pair of contour lines of the edge portions on both sides in the tire circumferential direction of the top surface of the low block are each formed by connecting 3 or more straight line portions in the tire radial direction, and when a straight line portion located at the 1 st from the boundary of each contour line is set as a first straight line portion, a straight line portion located at the 2 nd is set as a second straight line portion, and a straight line portion located at the 3 rd is set as a third straight line portion, the block pair includes the following straight line portions: the first linear portions extend in the same direction at an angle difference of 15 ° or less from each other, the second linear portions extend in the same direction at an angle difference of 15 ° or less from each other, and the third linear portions extend in different directions at an angle difference of more than 15 ° from each other.

ADVANTAGEOUS EFFECTS OF INVENTION

In the present invention, when the sidewall regions are provided with the sidewall blocks to improve the running performance on the unpaved road, by providing the difference in the rise height between the adjacent sidewall blocks (high block and low block) in the tire circumferential direction and bringing part of these high block and low block into contact to make these blocks function substantially as 1 large block as described above, the excellent edge effect is maintained by the unevenness of the block top surface to exhibit the running performance on the unpaved road well, and the block strength is improved to improve the cut resistance. By configuring the contour lines of the blocks as described above, the grooves formed by the straight advancing portions can exhibit excellent soil discharge performance in the portions where the straight portions extend substantially in parallel (the portions where the angular difference is within 15 °), and the structure where the high blocks and the low blocks are partially in contact can be reliably formed in the portions where the straight portions are not substantially parallel (the portions including the straight portions where the angular difference exceeds 15 °), and the running performance and the cut resistance on the unpaved road can be effectively improved.

In the present invention, it is preferable that the third linear portion located on the other of the high block and the low block in at least one of the high block and the low block included in the block pair extends toward the other of the high block and the low block. By configuring the third straight portion in this manner, a part of one of the high block and the low block protrudes in the circumferential direction toward the other, and the high block and the low block are in contact with each other, so that the block shape is improved, and the running performance and the cut resistance on the unpaved road can be effectively improved.

In the present invention, it is preferable that the difference in the height of the high block and the low block included in the block pair is 0.5mm or more and 4.0mm or less. Thus, the uneven shape formed by the top surface of the high block and the top surface of the low block is improved, and it is advantageous to achieve both the running performance on the unpaved road and the cut resistance.

In the present invention, it is preferable that the area of the top surface of one of the high block and the low block included in the block pair is 30% to 70% of the area of the top surface of the other. In particular, it is preferable that the top surface of the lower block included in the block pair has an area of 30% to 70% of the area of the top surface of the upper block. By setting the sizes of the high blocks and the low blocks in an appropriate range in this way, the running performance and the cut resistance on the unpaved road can be effectively improved.

In the present invention, it is preferable that a plurality of shoulder blocks arranged in the tire circumferential direction and a shoulder lateral groove extending in the tire width direction between the shoulder blocks adjacent in the tire circumferential direction are provided in a shoulder region adjacent to the inner side in the tire width direction of the boundary, and the sidewall groove is disposed at an extended position of the shoulder lateral groove. By arranging the shoulder transverse grooves and the side grooves substantially continuously and arranging the side blocks on the outer sides of the shoulder blocks in the tire width direction in this manner, the positional relationship of these blocks and grooves becomes favorable, and the running performance on unpaved roads can be effectively improved.

In the present invention, it is preferable that the tire-radial-direction innermost end of the sidewall block is present in a range of 30% to 60% of the tire sectional height from the tire equator position toward the tire-radial-direction inner side. By arranging the side blocks in the tire radial direction in an appropriate range of the sidewall portion in this way, when the tire is buried in mud or the like during running on an unpaved road, the side blocks can be in good contact with the road surface, and the running performance on the unpaved road can be effectively improved. In addition, since the size of the sidewall block can be appropriately secured, it is advantageous to improve the cut resistance by securing the block rigidity.

In the present invention, it is preferable that the total area of the high blocks is 32% to 52% with respect to the area of the sidewall region between the boundary and the tire radial direction innermost end of the sidewall block, the total area of the low blocks is 13% to 33% with respect to the area of the sidewall region between the boundary and the tire radial direction innermost end of the sidewall block, and the total area of the sidewall grooves is 25% to 45% with respect to the area of the sidewall region between the boundary and the tire radial direction innermost end of the sidewall block. By optimizing the balance of the elements provided in the sidewall region in this way, the running performance and cut resistance on an unpaved road can be effectively improved.

In the present invention, the "ground contact ends" refer to both end portions in the tire axial direction of a ground contact region formed when a normal load (japanese: normal weight load) is applied while a normal internal pressure (japanese: normal weight) is applied to a flat surface in a state where the tire rim is assembled to a normal rim (japanese: normal weight リム). "regular Rim" means a Rim specified per tire in a standard system including a standard on which tires are based, for example, a standard Rim (japanese: pre-registration リム) in case of JATMA, a "Design Rim" in case of TRA, or a "Measuring Rim" in case of ETRTO. The "normal internal PRESSURE" is an air PRESSURE determined for each TIRE in a standard system including standards based on TIREs, and is a maximum value described in a table "TIRE loads limit under VARIOUS COLD INFLATION PRESSURES" in case of JATMA, maximum air PRESSURE (japanese: highest altitude emanation PRESSURE) in case of TRA, and "INFLATION PRESSURE" in case of ETRTO, but is set to 180kPa in case of a passenger vehicle. The "normal LOAD" is a LOAD that is determined for each TIRE according to each standard in a standard system including standards based on which TIREs are based, and is a maximum LOAD CAPACITY (in japanese: maximum negative LOAD CAPACITY) in the case of JATMA, a maximum value described in a table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and a LOAD CAPACITY in the case of ETRTO, but is set to a LOAD corresponding to 88% of the LOAD.

Drawings

Fig. 1 is a radial cross-sectional view of a pneumatic tire constituted by an embodiment of the present invention.

Fig. 2 is a front view showing a tread surface of a pneumatic tire constituted by an embodiment of the present invention.

Fig. 3 is an explanatory view showing an enlarged view of a main part of a pneumatic tire according to an embodiment of the present invention.

Fig. 4 is an explanatory diagram showing the pair of blocks of fig. 3 extracted.

Fig. 5 is an explanatory diagram showing an example of a pair of blocks according to another embodiment of the present invention.

Detailed Description

Hereinafter, the structure of the present invention will be described in detail with reference to the accompanying drawings.

As shown in fig. 1, the pneumatic tire of the present invention includes a tread portion 1, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed on the inner side of the sidewall portions 2 in the tire radial direction. In fig. 1, reference symbol CL denotes a tire equator, and reference symbol E denotes a ground contact end. Fig. 1 is a meridian cross-sectional view and is not depicted, but the tread portion 1, the sidewall portion 2, and the bead portion 3 each extend in the tire circumferential direction to be annular, thereby constituting a basic structure of the annular shape of the pneumatic tire. In the following, the description using fig. 1 is based on the illustrated meridian cross-sectional shape, but each tire constituting member extends in the tire circumferential direction and is annular.

A carcass layer 4 is provided between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the vehicle inner side to the outer side around bead cores 5 disposed in the respective bead portions 3. Further, a bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is enclosed by the main body portion and the folded-back portion of the carcass layer 4. On the other hand, a plurality of (2 in fig. 1) belt layers 7 are embedded on the outer circumferential side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and is disposed between the layers such that the reinforcing cords intersect with each other. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in the range of, for example, 10 ° to 40 °. Further, a belt reinforcing layer 8 is provided on the outer peripheral side of the belt layer 7. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 8, the angle of the organic fiber cord with respect to the tire circumferential direction is set to, for example, 0 ° to 5 °.

The present invention is applied to a pneumatic tire having such a general cross-sectional structure, but the basic structure thereof is not limited to the above structure.

The present invention relates to a shoulder region and a sidewall region (particularly, a sidewall region) described later, and therefore the detailed shape of the tread portion 1 is not limited to the example of fig. 2 as long as it is a tread pattern mainly composed of blocks suitable for unpaved roads.

A pair of main grooves 10 extending in the tire circumferential direction on both sides of the tire equator CL is formed in the surface of the tread portion 1 of the pneumatic tire shown in fig. 2. The maximum width of the main grooves 10 is, for example, 9mm to 20mm, and the groove depth is, for example, 10mm to 18 mm. As will be described later, the main grooves 10 have a zigzag shape in which portions extending straight in a predetermined direction are connected via a bending point.

The 3-row land portions defined by these main grooves 10 are further divided into blocks 20 by various grooves, and the entire tread pattern is a block pattern based on the blocks 20. In the illustrated example, among the plurality of blocks 20, a shoulder block 21 is defined on the outer side in the tire width direction of the pair of main grooves, and a center block 22 is defined between the pair of main grooves. The shoulder blocks 21 are divided by shoulder transverse grooves 31 extending from the main groove 10 beyond the ground contact edge E, and a plurality of shoulder blocks 21 are arranged in the tire circumferential direction. The center blocks 22 are divided by center lateral grooves 32a connecting the pair of main grooves 10 and extending in the tire width direction and auxiliary grooves 32b connecting the center lateral grooves 32a adjacent to each other in the tire circumferential direction, and 2 rows of center blocks 22 arranged on both sides of the auxiliary grooves 32b are repeatedly arranged in the tire circumferential direction. Sipes 41 and narrow grooves 42 can be provided on the tread surface of the center block 22, the tread surface of the shoulder block 21, and the outer side surface in the tire width direction.

Among the lateral grooves of the block 20, the shoulder lateral grooves 31 are preferably divided into land portions defined by the main grooves 10, and have a groove width of, for example, 9mm to 20mm and a groove depth of, for example, 12mm to 17mm, and the center lateral groove 32a is preferably divided into a groove width of, for example, 7mm to 13mm and a groove depth of, for example, 11mm to 14 mm. In particular, the shoulder lateral grooves 31 preferably have the same groove depth as the main grooves 10. The auxiliary groove 32b preferably has a groove width of 7mm to 10mm and a groove depth of 9mm to 12mm, for example. The randomly formed sipe 41 is a fine groove having a groove width of, for example, 0.5mm to 2.0mm and a groove depth of, for example, 2mm to 15mm, and the randomly formed fine groove 42 is a groove having a groove width and a groove depth sufficiently smaller than those of the main groove 10 and the lateral groove, and has a groove width of, for example, 0.5mm to 4.0mm and a groove depth of, for example, 2mm to 15 mm.

In the sidewall region adjacent to the outer side in the tire width direction of the shoulder region where the shoulder block 21 is provided, as shown in fig. 3 and 4, a sidewall land portion rising from the outer surface of the sidewall portion 2 is provided, and the sidewall land portion is further divided into a plurality of sidewall blocks 23 by a sidewall groove 33. In the illustrated example, at the boundary between the side surface on the outer side in the tire width direction of the shoulder block 21 and the top surface of the sidewall block 23 (the boundary between the shoulder region and the sidewall region), there is a ridge 24 which rises more than these side surface and top surface and extends over the entire circumference of the tire. Therefore, if the viewing direction is changed, the shoulder region is adjacent to the inner side of the bead 24 (boundary between the shoulder region and the sidewall region) in the tire width direction, and the sidewall region is adjacent to the inner side of the bead 24 (boundary between the shoulder region and the sidewall region) in the tire radial direction, and the shoulder block 21 and the sidewall block 23 are provided in the shoulder region and the sidewall region, respectively.

As shown in the illustrated example, the sidewall grooves 33 defining the sidewall blocks 23 are preferably located on the extension of the shoulder transverse grooves 31 and extend substantially continuously. Further, the side blocks 23 are preferably arranged at extended positions on the outer side in the tire width direction of each shoulder block 21 in accordance with the positional relationship between the grooves. Further, as shown in fig. 2, the side blocks 23 and the side grooves 33 are located on the outer sides in the tire width direction of the shoulder blocks 21 and the shoulder lateral grooves 31 when viewed from the tread surface side of the tread portion 1, but as shown in fig. 3 and 4, the side blocks 23 and the side grooves 33 are located on the inner sides in the tire radial direction of the shoulder blocks 21 and the shoulder lateral grooves 31 when viewed from the side of the sidewall portion 2. The fact that the grooves are located on the extension line means that at least a part of virtual grooves obtained by extending the target grooves respectively overlap each other in the groove width direction.

In the present invention, the side blocks 23 include 2 kinds of blocks of a high block 23H having a relatively large ridge height and a low block 23L having a relatively small ridge height. These high blocks 23H and low blocks 23L are alternately arranged in the tire circumferential direction. When the high blocks 23H and the low blocks 23L adjacent to each other in the tire circumferential direction are the block pair B, the inner ends of the sidewall grooves 33 located between the high blocks 23H and the low blocks 23L included in the block pair B in the tire radial direction are closed by contacting a part of the high blocks 23H and the low blocks 23L included in the block pair B. Hereinafter, the sidewall groove 33 having the tire radial direction inner end closed may be referred to as a closed groove 33A, and the sidewall groove 33 having the tire radial direction inner end opened between the block pairs B adjacent to each other in the tire circumferential direction may be referred to as an open groove 33B.

In each block pair B, a pair of contour lines of the edge portions on both sides in the tire circumferential direction of the top surface of the high block 23H and a pair of contour lines of the edge portions on both sides in the tire circumferential direction of the top surface of the low block 23H are each formed by connecting 3 or more straight portions in the tire radial direction. When the straight line portion located at the 1 st from the boundary of the contour lines is defined as the first straight line portion L1, the straight line portion located at the 2 nd is defined as the second straight line portion L2, and the straight line portion located at the 3 rd is defined as the third straight line portion L3, all of the first straight line portions L1 included in the block pair B extend in the same direction at an angle difference of within 15 ° from each other and are substantially parallel to each other. Further, the present invention also includes the following linear portions: the second linear portions L2 and the third linear portions L3 extend in the same direction and substantially in parallel with each other with an angular difference of 15 ° or less, while the second linear portions L2 and the third linear portions L3 extend in different directions with an angular difference of more than 15 °.

For example, in the example of fig. 4, all the first straight portions L1 included in the block pair B extend in the same direction at an angular difference of 15 ° or less from each other. All the second linear portions L2 included in the block pair B extend in the same direction at an angle difference of 15 ° or less from each other, and are substantially parallel to each other. On the other hand, the third linear portions L3 included in the pair of blocks B include linear portions extending in different directions with an angular difference exceeding 15 °, and the third linear portions L3 extend in different directions from each other.

In contrast, in the example of fig. 5, all the first straight portions L1 included in the block pair B extend in the same direction at an angular difference of 15 ° or less from each other. All the third linear portions L3 included in the block pair B extend in the same direction at an angle difference of 15 ° or less from each other, and are substantially parallel to each other. On the other hand, the second linear portions L2 included in the pair of blocks B include linear portions extending in different directions with an angular difference exceeding 15 °, and the second linear portions L2 extend in different directions from each other.

When the first to third linear portions L1 to L3 are continuous in the tire radial direction, the linear portions may be smoothly continuous with each other via an arc. For example, the first straight line portion L1 and the second straight line portion L2 on the side of the closed groove 33A of the high block 23H in fig. 4, the second straight line portion L2 and the third straight line portion L3 on the side of the closed groove 33A of the low block 23L in fig. 4, the first straight line portion L1 and the second straight line portion L2 on the side of the open groove 33B of the low block 23L in fig. 4, the first straight line portion L1 and the second straight line portion L2 on the side of the closed groove 33A of the high block 23H in fig. 5, and the first straight line portion L1 and the second straight line portion L2 on the side of the open groove 33B of the low block 23L in fig. 5 are smoothly continuous via arcs.

Since the pair of blocks B is configured in this way, it is possible to exhibit an excellent edge effect by the unevenness of the block top surface due to the difference in the rise height between the side blocks 23 (the high blocks 23H and the low blocks 23L) adjacent in the tire circumferential direction, and it is possible to exhibit the traveling performance on an unpaved road well. On the other hand, since the high block 23H and the low block 23L are partially in contact with each other and these blocks (block pair B) substantially function as 1 large block, the block strength can be increased to improve the cut resistance. Since the contour lines of the blocks are configured as described above, the grooves formed by the straight portions can exhibit excellent soil discharge performance at portions where the straight portions extend substantially in parallel (portions of the first straight portion L1 and the second straight portion L2 in the example of fig. 4, and portions of the first straight portion L1 and the third straight portion L3 in the example of fig. 5). Further, in the portions where the straight portions are substantially not parallel (the third straight portion L3 in the example of fig. 4 and the second straight portion L2 in the example of fig. 5), the structure in which the portions of the high block 23H and the low block 23L are in contact with each other can be reliably formed, and the traveling performance and the cut resistance on the unpaved road can be effectively improved.

In the portions where the straight portions extend substantially in parallel (the portions of the first straight portion L1 and the second straight portion L2 in the example of fig. 4, and the portions of the first straight portion L1 and the third straight portion L3 in the example of fig. 5), if the angle difference between the straight portions exceeds 15 °, the groove width formed by the straight portions becomes non-constant, and the effect of improving the soil discharge performance cannot be obtained. In the present invention, of the first to third linear portions L1 to L3 included in 3 or more linear portions constituting the contour line as described above, 2 types of linear portions (the first linear portion L1 and the second linear portion L2 in the example of fig. 4, and the first linear portion L1 and the third linear portion L3 in the example of fig. 5) extend substantially in parallel, but if there are less than 2 types of linear portions extending substantially in parallel, the groove shape becomes inappropriate, and the effect of improving the soil discharge performance cannot be obtained.

When comparing the embodiments of fig. 4 and 5, the embodiment of fig. 4 including the linear portions extending in different directions in the third linear portion L3 is preferable. In particular, as shown in the drawing, it is preferable that the third linear portion L3 on the closed groove 33A side of the high block 23H included in the block pair B extends toward the low block 23L. By configuring the third straight line portion L3 in this manner, a part of the high block 23H protrudes in the circumferential direction toward the low block 23L, and the blocks are in contact with each other, so that the block shape is improved, and the running performance and the cut resistance on the unpaved road can be effectively improved. In addition, in contrast to the illustrated structure, the third linear portion L3 on the closed groove 33A side of the lower block 23L included in the block pair B may extend toward the upper block 23H. In this case as well, since a part of the low block 23L protrudes in the circumferential direction toward the high block 23H and these blocks contact each other, the running performance and the cut resistance on the unpaved road can be effectively improved.

The height of the raised portion of the sidewall block 23 is preferably set to 3mm to 7mm, for example. Thus, when the vehicle travels on an unpaved road, the side blocks 23 appropriately contact the road surface, and the traveling performance of the side blocks 23 can be satisfactorily exhibited. Further, the difference in the height of the rise of the high block 23H and the low block 23L included in the block pair B is preferably set to 0.5mm or more and 4.0mm or less. This makes the uneven shape formed by the top surfaces of the high blocks 23H and the low blocks 23L good, and contributes to both the traveling performance on unpaved roads and the cut resistance. If the difference in the rise heights is less than 0.5mm, the rise heights are substantially the same, and therefore, an edge effect based on the difference in the rise heights cannot be obtained, and the effect of improving the running performance on the unpaved road cannot be sufficiently obtained. If the difference in the rise height exceeds 4.0mm, it becomes difficult to sufficiently secure the block strength of the low block 23L, and it becomes difficult to sufficiently improve the cut resistance.

The area of the top surface of one of the high block 23H and the low block 23L included in the block pair B is preferably 30% to 70% of the area of the top surface of the other. By providing the difference in area (difference in block volume) between the high blocks 23H and the low blocks 23L in this way, the unevenness of the sidewall blocks 23 becomes complicated, which is advantageous in improving the running performance on unpaved roads. In particular, it is preferable that the high block 23H is relatively large, and the area of the top surface of the low block 23L included in the block pair B is preferably 30% to 70% of the area of the top surface of the high block 23H. If the area of the block having a relatively small area of the top surface is less than 30% of the area of the other top surface, the block having a relatively small area of the top surface becomes too small and the block strength decreases, so that it is difficult to sufficiently improve the cut resistance. If the area of the block having a relatively small area of the top face exceeds 70% of the area of the other top face, the difference in area becomes small, and blocks having the same area of the top face are arranged in the circumferential direction, so that the unevenness of the sidewall block 23 cannot be sufficiently complicated, and the effect of improving the running performance on the unpaved road is limited.

The total area of the high blocks 23H is preferably 32% to 52% of the area of the sidewall region between the boundary and the innermost end of the sidewall block in the tire radial direction (see the broken lines in fig. 4 and 5), the total area of the low blocks 23L is preferably 13% to 33% of the area of the sidewall region between the boundary and the innermost end of the sidewall block in the tire radial direction (see the broken lines in fig. 4 and 5), and the total area of the sidewall grooves 33 is preferably 25% to 45% of the area of the sidewall region between the boundary and the innermost end of the sidewall block in the tire radial direction (see the broken lines in fig. 4 and 5). By optimizing the balance of the elements provided in the sidewall region in this way, the running performance and cut resistance on an unpaved road can be effectively improved. The total area of the high blocks 23H and the low blocks 23L is the sum of the areas of the top surfaces of the respective blocks, and the total area of the sidewall grooves 33 is the sum of the areas of the bottom surfaces of the respective grooves. If the area of each element deviates from the above range, the balance of each element in the sidewall region is lost, and it is difficult to highly balance the running performance and cut resistance on the unpaved road.

The sidewall blocks 23 are preferably disposed in an appropriate region in the tire radial direction so as to be appropriately in contact with the road surface when the tire is buried in mud or the like during running on an unpaved road. Specifically, the tire-radial-direction innermost end of the side block 23 is preferably present in a range of 30% to 60% of the tire section height SH from the tire equator CL position toward the tire-radial-direction inner side. In other words, the distance D from the tire equator CL to the tire radial direction innermost end of the side block 23 is preferably 30% to 60% of the tire section height SH. By disposing the sidewall blocks 23 in an appropriate range in the tire radial direction of the sidewall portion 2 in this way, the running performance on unpaved roads can be effectively improved. In addition, since the size of the side block 23 can be appropriately secured, it is advantageous to secure block rigidity and improve cut resistance. If the distance D is less than 30% of the tire section height SH, the side blocks 23 become small, so it is difficult to maintain good cut resistance. If the distance D exceeds 60% of the tire section height SH, the sidewall blocks 23 become excessively large, and may affect the normal running performance. In connection with the arrangement of the side blocks 23, it is preferable that the boundary between the shoulder region and the side region is located within a range of 20% to 25% of the tire section height SH from the tire equator CL position toward the tire radial direction inner side, regardless of the presence or absence of the bead 24.

As shown in the drawing, a cutout (japanese utility model: decision れ)21a which is processed in a concave shape and is recessed more inward in the tire width direction than the edge on the tire width direction outer side of one of 1 pair of shoulder blocks 21 located on the tire width direction inner sides of the block pairs B may be provided on the edge on the tire width direction outer side of the other block. This makes the shape of the edge portion of the shoulder block 21 in the tire circumferential direction complicated, and therefore contributes to improvement of the running performance on unpaved roads.

As shown in the illustrated example, when the narrow groove 42 is provided in the side surface of the shoulder block 21 on the outer side in the tire width direction, the narrow groove 42 is preferably provided also in the top surface of the side block 23. The narrow groove 42 provided in the sidewall block 23 preferably extends inward in the tire radial direction from the position of the inner end of the narrow groove 42 provided in the tire width direction outer side surface of the shoulder block 21 in the tire radial direction. The narrow grooves 42 provided in the sidewall blocks 23 preferably extend in the same direction at an angle difference of 15 ° or less with respect to the first straight line portion L1. This can add the soil discharge property and the edge effect by the narrow grooves 42, and is advantageous for improving the traveling performance on the unpaved road.

The top surface of the side block 23 may be provided with a linear protrusion 50 having a width of, for example, 0.5mm to 2.0mm and a protruding height from the block top surface of, for example, 0.5mm to 1.5 mm. In the illustrated example, the linear protrusions 50 extending along the contour line of each sidewall block 23 in a range of 5mm to 20mm away from the contour line, and the linear protrusions 50 extending so that one end thereof is connected to the narrow groove 42 and passes through the middle position of a pair of contour lines on both sides of the sidewall block 23 in the tire circumferential direction at the center position of the sidewall block 23 in the tire circumferential direction are provided. Such linear protrusions 50 also function as edge components, and therefore contribute to improvement in running performance on unpaved roads.

As shown in fig. 2, the sidewall blocks 23 described above can exhibit the above-described effects if they are provided in at least one of the sidewall regions on both sides in the tire width direction (in the illustrated example, the right sidewall region). Of course, the sidewall blocks 23 described above may be applied to both of the sidewall regions on both sides in the tire width direction. Further, as shown in fig. 2, by applying the above-described sidewall blocks 23 to one sidewall region and adopting different shapes to the other sidewall region, it is also possible to make the sidewall region on one side and the sidewall region on the other side in the tire width direction specialized for different performances.

Examples

A tire size LT265/70R 17121Q, a tire having the basic structure illustrated in fig. 1, and adjusted based on the tread pattern of fig. 2, and including "presence/absence of contact between a high block and a low block adjacent to each other in the tire circumferential direction in a block pair", "difference in the rise height between a high block and a low block constituting a block pair", "relationship in the extension direction of a pair of contour lines (first straight line portion, second straight line portion, and third straight line portion) of edge portions on both sides in the tire circumferential direction of top surfaces of a high block and a low block included in a block pair", "correspondence with drawings", "proportion of the area of the top surface of a block included in a block pair, the area of which the top surface is relatively small with respect to the area of the top surface of a block, the proportion of the total area of blocks, low blocks, and side grooves with respect to the area of a side wall region", were prepared, "the ratio (D/SH x 100%) of the distance D from the tire equator CL position to the tire radial direction innermost end of the sidewall block with respect to the tire section height SH" is set as shown in tables 1 to 2 for 16 kinds of pneumatic tires of comparative examples 1 to 3 and examples 1 to 13.

In the column "presence or absence of contact between high and low blocks" in tables 1 to 2, the case where the high block and the low block adjacent to each other in the circumferential direction of the tire in the block pair are in contact as shown in fig. 4 and 5 is indicated as "presence", and the case where all of the first to third linear portions extend parallel to each other and all of the side grooves are open to the inside in the radial direction of the tire without being closed is indicated as "absence". In addition, even in the case where there is no difference in the rise height as in comparative examples 1 to 2, the block at the position corresponding to the high block in fig. 4 is regarded as the high block for convenience, and the block corresponding to the low block in fig. 4 is regarded as the low block for convenience.

In the column of the first to third linear portions in tables 1 to 2, the case where the linear portions extend in the same direction at an angle difference of 15 ° or less is referred to as "parallel", and the case where the linear portions extend in different directions at an angle exceeding 15 ° is referred to as "different directions". For convenience, the column "corresponding to the drawings" in tables 1 to 2 indicates "fig. 4'" in which the block shape in fig. 4 is used as a base, all of the first to third linear portions extend parallel to each other, and all of the side grooves are open to the inner side in the tire radial direction without being closed. For convenience, the case where the block shape of fig. 4 is used as a base key and there is no difference in the height of the ridge between the portion corresponding to the high block and the portion corresponding to the low block is represented as "fig. 4".

In the column of "the relationship of the size of the top surface" in tables 1 to 2, the case where the top surface of the high block has a larger area than the top surface of the low block is expressed as "high > low", and the case where the top surface of the low block has a larger area than the top surface of the high block is expressed as "high < low". In the column "total area" in tables 1 to 2, in the case where there is no difference in the ridge height as in comparative examples 1 to 2, the sum of the areas of the top surfaces of all the blocks is described in the column "high block", and the column "low block" is referred to as an empty column.

These pneumatic tires were evaluated for starting performance and cut resistance on unpaved roads by the following evaluation methods, and the results are shown in tables 1 to 2.

Starting property

Each test tire was assembled to a wheel having a rim size of 17 × 8J, mounted on a test vehicle (four-wheel-drive SUV) with the air pressure set at 350kPa, and subjected to sensory evaluation by a test driver on a test road composed of an unpaved road (gravel road surface). The evaluation results are expressed as an index with the value of comparative example 1 set to 100. The larger the index value, the more excellent the starting performance on the unpaved road. When the index value is less than "105", the difference from the conventional level (comparative example 1 as a reference) is small, which means that the effect of improving the starting performance on the unpaved road cannot be sufficiently obtained.

Cut resistance

Each test tire was assembled to a wheel having a rim size of 17 × 8J, mounted on a test vehicle (four-wheel-drive SUV) with an air pressure of 350kPa, and after running 1000km on an off-road durable road, the total length of the cut generated at the side wall portion was measured. The evaluation results are expressed as an index in which the reciprocal of the measurement value of comparative example 1 is 100. The larger the index value, the smaller the total length of cutting, meaning the more excellent the cut resistance. Further, if the index value is less than "105", it means that the difference from the conventional level (comparative example 1 as a reference) is small, and the effect of improving the cut resistance cannot be sufficiently obtained.

[ Table 1]

[ Table 2]

As is clear from tables 1 to 2, in each of examples 1 to 13, the starting performance and the cut resistance on the unpaved road were effectively improved as compared with comparative example 1. Further, only the starting performance on a gravel road surface was evaluated, but the tire of the present invention can exhibit excellent starting performance because it effectively acts on mud, rocks, snow, and the like on a road surface even when the tire is driven on other unpaved roads (muddy roads, rocky roads, snow roads, and the like).

On the other hand, in comparative example 2, although the side blocks adjacent to each other in the tire circumferential direction were in contact with each other, there was no difference in the rise height between these blocks, and therefore the effect of improving the starting performance and the cut resistance on the unpaved road could not be sufficiently obtained. In comparative example 3, since the adjacent high blocks and low blocks in the tire circumferential direction were not in contact with each other, the effect of improving the starting performance and the cut resistance on the unpaved road could not be sufficiently obtained.

Description of the reference numerals

1 tread part

2 side wall part

3 bead portion

4 carcass ply

5 bead core

6 bead filler

7 belted layer

8-belt reinforcement layer

10 main groove

20 blocks

21 shoulder block

21a cutout

22 center block

23 side wall block

24 protruding strip

31 tire shoulder transverse groove

32a central transverse groove

32b auxiliary groove

33 side wall groove

41 sipe

42 thin groove

50 linear convex part

B block pair

L1 first straight line part

L2 second straight line part

L3 third straight line part

CL tire equator

E ground terminal

Claims

1. A pneumatic tire is provided with: a tread portion extending in a tire circumferential direction and having a ring shape; a pair of sidewall portions disposed on both sides of the tread portion; and a pair of bead portions disposed on the inner side in the tire radial direction of the side wall portions,

the pneumatic tire is characterized in that it is,

a plurality of sidewall grooves extending in the tire radial direction and a plurality of sidewall blocks partitioned by the sidewall grooves and rising from the outer surface of the sidewall portion are provided in a sidewall region adjacent to the inner side in the tire radial direction of the boundary between the tread portion and the sidewall portion,

the side blocks include 2 blocks of high blocks having a relatively large rise height and low blocks having a relatively small rise height, which are alternately arranged in the tire circumferential direction, and when the high blocks and the low blocks adjacent in the tire circumferential direction are set as a block pair, a part of the high blocks and the low blocks included in the block pair are in contact, whereby the tire radial direction inner end of the side groove between the high blocks and the low blocks included in the block pair is closed,

in each block pair, a pair of contour lines of the edge portions on both sides in the tire circumferential direction of the top surface of the high block and a pair of contour lines of the edge portions on both sides in the tire circumferential direction of the top surface of the low block are each formed by connecting 3 or more straight line portions in the tire radial direction, and when a straight line portion located at the 1 st from the boundary of each contour line is set as a first straight line portion, a straight line portion located at the 2 nd is set as a second straight line portion, and a straight line portion located at the 3 rd is set as a third straight line portion, the block pair includes the following straight line portions: the first linear portions extend in the same direction at an angle difference of 15 ° or less from each other, the second linear portions extend in the same direction at an angle difference of 15 ° or less from each other, and the third linear portions extend in different directions at an angle difference of more than 15 ° from each other.

2. A pneumatic tire according to claim 1,

a third linear portion located on the other of the high block and the low block in at least one of the high block and the low block included in the block pair extends toward the other of the high block and the low block.

3. A pneumatic tire according to claim 1 or 2,

the difference in the height of the high block and the low block included in the block pair is 0.5mm or more and 4.0mm or less.

4. A pneumatic tire according to any one of claims 1 to 3,

the area of the top surface of one of the high block and the low block included in the block pair is 30% to 70% of the area of the top surface of the other.

5. A pneumatic tire according to claim 4,

the area of the top surface of the low block included in the block pair is 30% to 70% of the area of the top surface of the high block.

6. A pneumatic tire according to any one of claims 1 to 5,

in a shoulder region adjacent to the inner side in the tire width direction of the boundary, a plurality of shoulder blocks arranged in the tire circumferential direction and a shoulder lateral groove extending in the tire width direction between the shoulder blocks adjacent in the tire circumferential direction are provided, and the sidewall groove is disposed at an extended position of the shoulder lateral groove.

7. A pneumatic tire according to any one of claims 1 to 6,

the innermost end of the sidewall block in the tire radial direction is located in a range of 30-60% of the tire section height from the tire equator position toward the tire radial direction inner side.

8. A pneumatic tire according to any one of claims 1 to 7,

the total area of the high blocks is 32-52% of the area of a sidewall area between the boundary and the innermost end of the sidewall block in the tire radial direction, the total area of the low blocks is 13-33% of the area of a sidewall area between the boundary and the innermost end of the sidewall block in the tire radial direction, and the total area of the sidewall grooves is 25-45% of the area of a sidewall area between the boundary and the innermost end of the sidewall block in the tire radial direction.